Combustion apparatus



Aug. 2, 1966 D. E. SAFFORD COMBUSTION APIARTUSl 2 Sheets-Sheet 1 Filed Aim-11 1o. 1964 INVENTOR. DONALD E. SAFFORD A TTORNE K5' 2 Sheets-Sheet 2 Filed April 1o, 1964 FIGB INVENTOR. DONALD E. SAF FORD BY /V/C A TTOR NE Y6' United States Patent O 3,263,978 COMBUSTION APPARATUS Donald E. Saiford, Park Forest, Ill., assignor to Sinclair Research, Inc., New York, N.Y., a corporation of Delaware Filed Apr. 10, 1964., Ser. No. 358,740 Claims. (Cl. 263-19) The present invention relates to a liquid fuel burner and more specifically to a burner of the type which has a spinning element for atomiza-tion of the fuel in the combustion chamber.

Liquid fuel burners of the type in which there is a motor driven spinning element into which the fuel is fed are well known. In such burners the fuel is thrown from the periphery of the Ispinner into a stream of air with such velocity to bring abou-t atomization of the fuel and mixing thereof with the air. Combustion of the fuel-air mixture occurs in the area surrounding the spinning element. Burners of this type have advantages among which are the following: fuel may be fed to the bu-rner by gravity or by a low pressure pump, thereby avoiding the need for expensive and complicated hi-gh pressure pumping equipment. Such 'burners as contrasted with spray nozzle burners are less likely to clog in as much as the fuel does not need to be forced through a small orifice at high pressure. In other words, the fuel delivery pressures prevailing in a spinner burner are of such a low order that comparatively large fluid passages, e.g. often on the order of about 1/s to `1/2 inch or more can be used.

Liquid fuel burners using a spinning element have also 'been modified to include an asbestos wicking against 'which the fuel is thrown. This wicking acts as a vaporizing or burning surface. However, as the fuel is being absorbed into this wick, fuel vaporization cools the wicking with resulting fuel coking. These coking tendencies preclude the burning of heavier No. 2 fuel oils in a burner of this type; kerosene is the preferred fuel. Also, the heretofore known liquid fuel burners have not provided sufficient combustion air control and, therefore, have experienced flame cooling at low firing rates. The cooled flame, of course, produces objectionable smoke and obnoxious odors.

It is an object of the present invention to utilize a superior vaporizing surface with heating of the surface to insure proper vaporiza-tion and buming of various grade fuel oils for complete combustion. It is a further object of the present invention to provide a novel combustion environment for clean, efficient, burning of kerosene, No. l or No. 2 fuel oil in low firing rate burners.

Burners in accordance with the present invention are highly desirable for low firing rate appliances, such as, water heater, incinerators, space heaters, etc. A further object of the present invention is to provide a novel pr-imary conibustion control located so as to govern the air lsupply to the arne to maintain proper flame temperature.

Generally, the present invention is directed to a liquid fuel burner which includes a cylindrical combustion chamber lined with a highly efficient, insulating low-heatsump material, e.g. a refractory material such as Fiberfrax to form a fire box. IFiberfrax is bonded aluminasilica fiber. The surface of the refractory material is then coated with a relatively low-porosity, non-absorbent material to form the internal impinging or vaporizing ice surface for the fuel such as Fiberfrax silica cement which hardens to a ceramic-like surface after r-ing. Other suitable compositions -for use as the internal impinging surfaceinclude those which may be cast at high temperatures and which have a dense non-absorbent surface or which may be glazed; stainless steel, for example, could be used. It is required, however that a high temperature insulation generally with a k factor less than about 5, be placed between the internal impinging surface and the combustion chamber wall. The fuel is thrown against this vaporizing sur-face by means of a slinger having a fuel opening of several millimeters and rotating within the combustion chamber or fire box. The slinger breaks the fuel stream into the form of relatively large droplets; however, since the heat from the combustion llame heats the impinging surface to a temperature of about 800 to 1600 F., the droplets of fuel are very rapidly vaporized when they impinge on the impinging surface. Additionally, should any coking tend to occur, the coke is burned off the hot impinging surface at these temperatures.

In association with the improved vaporizing surface of the burner, an iris-li-ke primary air control means having a pair of semi-circular washers that are adjustable through a scissors-like linkage can be used to control the amount of primary air introduced into the combustion chamber through closing of the annular combustion air supply oririce which commonly is concentric with the combustion chamber and the drive shaft for the atomizing element.

A heater according to the present invention is especially desirable in semi-enclosed areas such as repair shops, steel fabricating plants, etc., to supply hot air for heating. Also, plastic bubble enclosures or Itents, which` are 'becoming more common to permit year round construction, may be both inflated as well as heated by the hea-ter of the present invention.

Other objects and advantages will become apparent from the following description of a preferred embodiment of the present invention which is illustrated in the accompanying drawings.

FIGURE l is a cros-s sectional view of a heater in accordance with the present invention taken along section iine I-I in FIGURE `2.

FIGURE 2 is an end view taken along section line II-II of the FIGURE l.

FIGURE 3 is an over all View, partly broken away, of a portable unit employing a heater in accordance with the present invention.

Referring now to the drawing in greater detail it will 4be seen that the heater comprises an outer cylindrical sheet metal casing 10 (see FIGURE `1) which contains therein the combustion chamber 30. The metal casing 10 forms a passageway 12 through which air is supplied to the combustion chamber 30 by fan 14 which is driven by shaft y16 of motor 185 The motor 18 is supported inl casing 10 -by support elements 19. Atomizing element or slinger 20 is arranged within the combustion chamber 30 on the end of shaft 16 coaxially with the duct 10 and chamber 30. The slinger 20 is rota-ted by motor 18. A fuel passage 22 is arranged within the shaft -16 for conveying fuel to the slinger 20. The cylindrical combustion chamber 30 is formed of sheet metal and includes a fire box 32 formed of `an insulating, low-heat-pump refractory material, such -as lFiberfrax, and a vaporiZ-ing surface 34 on re box 32 formed by a coating of a relatively low porosity materi-al such as Fiberfrax cement applied to the re box 32. The chamber 30 is supported lin casing by elements 31. v

An air opening 35 for supplying primary combustion air to chamber 30 is provided around yand coaxially with shaft 16. Valve elements 40 and 42 (see FIGURE 2) control the amount of combustion air passing through opening 35. An ignition coil 36 is arranged in chamber 30 and connected with electrical leads 38. Leads 38 connect the coil to a suitable source vof current which heats the coil 36. The ignition coil 36 is used to start operation of the heater by igniting the fuel.

The valve for controlling the supply of primary combustion air through opening 35 comprises a pair of washerlike elements 40 and 42 as illustrated in FIGURE 2. These elements are pivotally supported in a scissors-like arrangement on the chamber 30, for example, at pivot point 44. Opening and closing of the valve is accomplished, for example, by handle portions on the elements 40 and 42 which extend through slot 41 in casing 10. The elements 40 and 42 may be held in the desired position by conventional means (not shown) such as notches in casing 10, etc.

FIGURE 3 illustrates a preferred heater embodiment for utilizing the improved burner illustrated in FIGURE 1. Like reference numerals are used to designate like parts in FIGURES l and 3. FIGURE 3 is a portable space heater incorporating the new burner concept within an outer casing 10, as shown in the break-away portion thereof. As illustrated, both the outer casing 10 and the combustion chamber 30 have nozzle portions, 64 and 66, respectively, for more ecient blending of the primary and secondary air streams which are drawn in through the open opposite end of the casing 10 and for directing the flow of hot air. The secondary air stream passes through the annular passageway 63 which surrounds the combustion chamber 30 within the outer casing 10.

The outer casing 10 of the space heater is pivotally supported at the rear on bracket 56 of the portable stand formed by the tubular frame including uprights 52 and 54 and brackets 56 and 57. The front portion of the casing 10 may be raised or lowered through rod 60. Rod 60 is pivotally secured to the casing 10 at point 61. A set screw arrangement 62 is provided to maintain casing 10 in the desired vertical position. A fuel tank 50 is suspended from the brackets 56 and 57. Fuel is supplied to the atomizer element 20 through fuel line 58 and passageway 22 by a pump means (not shown). Control panel '70 includes control members for operating the fuel pump (not shown) which supplies fuel from tank 50 to atomizer element 20 and for controlling the speed of motor 13 to control the amount of air supplied by the heater.

Combustion performance of the burner of the present invention with either kerosene or No. 2 fuel oil was signiiicantly improved as compared with known burner designs as shown by Table I. Odors were eliminated and As a comparison, a fuel oil heater similar in all respects to the present invention except omitting the shutter arrangement and utilizing an asbestos wicking was tested with a high and a low firing rate. The results are shown The addition of a primary air ycontrol valve and the novel liner in the combustion chamber results in a signicantly improved performance of the apparatus with both kerosene and No. 2 fuel oil. There is no odor and very little smoke with the heater in accordance with the present invention as lcompared with the heater using asbestos wicking.

I claim:

1. Com-bustion apparatus adapted for eiliciently burning liquid fuel which may be supplied at low pressure without objectionable smoke and/or odor, comprising means defining a combustion chamber, a lire box in said chamber formed of an insulating low-heat-sump refractory material having a surface coating thereon of a nonabsorbent, relatively low porosity material, a centrifugal fuel supply unit projecting into said chamber including a slinger arranged within said chamber and mounted on a rotatable shaft, means for rotating said shaft and means adapted to supply fuel to said slinger, said fuel being thrown from the rim of said slinger by centrifugal force to impinge upon said surface coating of the frebox, the heat from combustion within said chamber being adapted to heat said re ybox surface whereupon said fuel is rapidly vaporized when the same impinges upon said surface coating, means defining an air intake for said combustion chamber adjacent said slinger and surrounding said shaft and an air control means for said air intake adapted to be operated from without said combustion chamber consisting of a pair of washer-like closure elements pivotally connected together in a scissors-type linkage and surrounding said shaft outside of said combustion chamber and adjacent to said one end of the combustion chamber.

2. The compact combustion apparatus of claim 1 wherein said material is silica refractory material and said surface is formed by a silica coating on said material.

3. The 'compact combustion apparatus of claim 1 further including an ignition means arranged in said combustion chamber.

4. Compact combustion apparatus adapted for eiciently burning liquid fuel which may be supplied at low pressure without objectionable smoke and/or odor, comprising means defining a combustion chamber, a re box in said chamber adjacent one end thereof formed of an insulating low-heat-sump refractory material having a surface coating thereon of a relatively low porosity material, a casing surrounding said combustion chamber and forming therewith a secondary air passageway essentially surrounding said chamber, a centrifugal fuel supply unit projecting into said chamber including a slinger adapted to be rotated within said lire box, means for supplying fuel to said slinger, and means for rotating said slinger comprising an electric motor and a shaft extending substantially coaxial of said combustion chamber, said means for supplying fuel to said slinger including a passageway extending through said shaft to said slinger, the fuel being thrown from the rim of s-aid slinger by centrifugal force upon rotation of said shaft to impinge upon said surface coating of the fire box, the heat from combustion within said chamber being adapted to heat said fire box surface whereupon said fuel is rapidly vaporized as it impinges upon said surface coating, a primary air intake for said combustion chamber surrounding said shaft adjacent said slinger, an iris-like air control means for said primary air intake consisting of a pair of washer-like closure elements pivotally connected together in a scissors-type linkage and surrounding said shaft outside of said combustion charnber and adjacent to said one end of said combustion chamber, each of the closure elements having a handle portion which extends outwardly of said casing through an opening therein whereby said air control means is adapted to be operated from without said casing and a fan mounted on said shaft for supplying said primary and secondary air.

5"." The compact combustion apparatus of claim 4 wherein said refractory material is an alumina-silica material and said surface coating is a silica cement.

References Cited by the Examiner UNITED STATES PATENTS 1,655,016 1/1928 Laughlin et al. 1,881,260 10/1932 Bravun et al 158-4 2,280,638 4/1942 Ruif 158-77 2,330,129 9/ 1943 Lucas et al. 3,029,863 4/ 1962 Downs 158-4 3,151,614 10/1964 Mendelson 158-1 X JAMES W. WESTHAVER, Primary Examiner. 

1. COMBUSTION APPARATUS ADAPTED FOR EFFICIENTLY BURNING LIQUID FUEL WHICH MAY BE SUPPLIED AT LOW PRESSURE WITHOUT OBJECTIONABLE SMOKE AND/OR ODOR, COMPRISING MEANS DEFINING A COMBUSTION CHAMBER, A FIRE BOX IN SAID CHAMBER FORMED OF AN INSULATING LOW-HEAT-SUMP REFRACTORY MATERIAL HAVING A SURFACE COATING THEREON OF A NONABSORBENT, RELATIVELY LOW POROSITY MATERIAL, A CENTRIFUGAL FUEL SUPPLY UNIT PROJECTING INTO SAID CHAMBER INCLUDING A SLINGER ARRANGED WITHIN SAID CHAMBER AND MOUNTED ON A ROTATABLE SHAFT, MEANS FOR ROTATING SAID SHAFT AND MEANS ADAPTED TO SUPPLY FUEL TO SAID SLINGER, SAID FUEL BEING THROWN FROM THE RIM OF SAID SLINGER BY CENTRIFUGAL FORCE TO IMPINGE UPON SAID SURFACE COATING OF THE FIREBOX, THE HEAT FROM COMBUSTION WITHIN SAID CHAMBER BEING ADAPTED TO HEAT SAID FIRE BOX SURFACE WHEREUPON SAID FUEL IS RAPID- 